1. Field of the Invention
The present invention relates to a discharging system for correcting variations in remaining capacity between battery blocks forming a battery pack and an electric vehicle equipped with the discharging system.
2. Description of the Related Art
An electric vehicle, such as a pure electric vehicle (PEV) or a hybrid electric vehicle (HEV) that obtains vehicular driving force from an electric motor, has a secondary battery installed and the electric motor is driven by electric power stored in the secondary battery. Such an electric vehicle is equipped with regenerative braking, namely, a braking function having the electric motor function as a generator during vehicular braking where the kinetic energy of the vehicle is converted into electrical energy. The converted electrical energy is stored into the secondary battery and is reused when performing acceleration.
The secondary battery installed in such an above-mentioned electric vehicle is often configured as a battery pack in which multiple battery blocks are connected in series. The battery block is configured, for example, from multiple cells or multiple battery modules in which multiple cells are connected in series. In a secondary battery configured in this manner, variations in battery's capacitance or battery voltage may occur among battery blocks, such as due to operating environment.
Japanese Patent Laid-Open Publication H11-234917 discloses a technique for performing a comparison between an average no-load voltage of cell batteries forming the battery pack and a predetermined reference voltage while a hybrid electric vehicle is stopped, and performing variation correction on the basis of the comparison result.
Japanese Patent Laid-Open Publication 2002-354698 discloses a technique for controlling a power supply section to an ON state by a high level signal output from a microcomputer when capacitance adjustment of a battery pack is performed with a bypass resistor, and for performing capacitance adjustment until completed without interruption by continuously supplying power to the entire control circuit from the power supply section even after charging/discharging of the battery pack completes.
Japanese Patent Laid-Open Publication 2003-189490 discloses a technique for stopping the operation of all bypass circuits when the voltage or remaining capacity of an auxiliary device power source is less than or equal to a predetermined value in a system for driving a control apparatus controlling bypass circuits for performing an equalizing process to correct variations among cell batteries by supplying power from the auxiliary device power source.